1. Field of the Invention
This invention relates to a flame-retardant rubber composition for use in tires and interior members of railroad and automotive vehicles, building materials, conveyor belts and the like which is capable of preventing fire or fire spreading.
2. Description of the Related Art
Recently, it has been required that conveyor belts, hoses, packing and the like have flame retardance, particularly, when these members are used in a closed space, such as a mine, or in vehicles such as automobiles. Needless to say, durability and strength of these members are required in addition to flame retardance.
Heretofore, many flame-retardant rubber compositions have been prepared by adding various flame retardants such as halogens, metal hydroxides, phosphorus and the like to ordinarily used rubber compositions. In these cases, only the flame retardance or durability was sought to be improved and the achievement of flame retardance and durability or strength was not attempted.
In general, when a flame retardant is added to rubber, a greater amount of the flame retardant is required, so that the properties inherent to a rubber composition are not degraded.
In order to overcome such a problem, it has frequently been attempted to control the degradation of the properties at a minimum and attain a high flame retardance by the synergistic action of a combination of flame retardants or a combination of flame retardant and another substance. For instance, a combination of a halogen flame retardant and antimony oxide, a combination of a halogen flame retardant and metal hydroxide and the like have been used. However, these attempts are not yet sufficient.